1. Application of differential staining techniques and continued improvement of established methods are basic to all the projects conducted in the laboratory. 2. Human cytogenetic studies of patients with congenital and developmental disorders as well as studies of mutagen-induced chromosomal abnormalities are continuing. 3. Murine cytogenetic studies include evaluating of mitotic and meiotic chromosomes and karyotypic evaluation of cells in hematopoetic tissue regeneration experiments. These are part of projects utilizing the mouse as a model for human diseases. 4. Correlation of flow cytometric analysis with cytogenetic findings.